As sales rebound and customers queue up for trade credit again, your cash flow could be at risk. Not from customer defaults — the number of global corporations that defaulted on bonds this year stood at just 16 as of March 1, down from 35 at the same point last year — but from buyers taking their sweet time to pay for goods and services. According to the National Association of Credit Management, customers are disputing invoices and sellers are placing accounts for collection more often today than they were a year ago.

When a company can’t finance its working capital with a bank line, after all, trade credit is the next best thing. “You have to understand the risk of slow pay, because it’s a cost of doing business with that customer,” says Pam Krank, president of The Credit Department, an outsourcing firm.

How does a CFO analyze the risk of a customer exceeding payment parameters? If you have enough financial-performance data on a customer, 98% of the time the risk will show up in the numbers, says Jerry Flum, chief executive of CreditRiskMonitor.

Krank recommends studying the customer’s days sales outstanding. “If your customer doesn’t get paid by its customer for 80 days, you won’t get paid in 30,” she says. “The money doesn’t come out of nowhere.” It’s also smart to track trends such as the buildup of short-term debt, Flum says. “That’s always one of the clearest signs that a company is having covenant restrictions placed on its long-term debt,” he says.

But actually mitigating the risk of slow pay is harder. In a climate where revenue growth is paramount, “you can’t just say they’re high risk so we can’t sell to them,” Krank says. If your company has substantial profit margins, in fact, it may still make sense to green-light the sale, Flum says.

Securing the transaction — with a bank letter of credit, a Uniform Commercial Code agreement, or a joint check agreement — can be a workable compromise. A UCC filing says the product is the seller’s until the buyer pays for it in full. A joint check agreement, suitable when there is a distributor in the middle of the transaction, allows the seller’s name to appear on the check that is written by the end-user of the goods. That guarantees that the seller, not the distributor, gets paid first.

Salespeople may balk at these practices, but the nascent stage of a wobbly economic recovery is no time for CFOs to loosen up on receivables management. Instead, Krank says, they need to start asking an important question: “Why are we financing these companies?”